1. Technical Field of the Invention
The present invention relates to cellular telephone networks and, in particular, to the provision of a calling 5 service feature to a subscriber in connection with a cellular telephone call originally made through a switching node of the network that has not yet been upgraded to provide support for that particular calling service feature.
2. Description of Related Art
New calling service features are constantly being developed and implemented by cellular telephone network service providers. These calling service features are typically provided by the switching nodes within the cellular telephone network, and thus in order to offer the calling service feature to all subscribers regardless of location within the network each of the switching nodes must be upgraded to support the feature. Because of the large number of switching nodes present in the cellular telephone network, it is not possible for each of the switching nodes to be substantially simultaneously upgraded to provide the new calling service feature. Furthermore, in some instances it may not make economic sense to upgrade the switching node in view of the low incidence of traffic patterns involving such new service features.
A call made through a switching node that has not yet been upgraded cannot initiate those new calling service features. It would be an advantage for that time period during which the upgrading of all switching nodes within the network has not been completed, if such new calling service features could be offered and provided to all subscribers regardless of either the mobile station location within the cellular telephone network or the upgrade status of the switching node that originally handles the call.